Seeing the ebook of Alan Hollinghurst's The Stranger's Child was 20p on Amazon, I snapped it up. Who wouldn't? A 564-page slice of literary fiction by one of Britain's finest novelists, heralded by the critics as "masterly" and controversially not shortlisted for last year's Booker, yours for the price of an onion.

But the thrill of a bargain soon gave way to post-purchase guilt. After all, there's no such thing as a cheap ebook. Seduced by predatory pricing, I had put selfish short-term gain over the long-term interests of civilisation: hastening the demise of bookshops and publishers.

This was too much for my conscience to bear, so my feelings turned to resentment. I would happily have paid 30 times as much for that ebook. How was I allowed to pay so little? Perhaps it was a glitch, the same malfunctioning algorithm that inflated the price of science textbook The Making of a Fly to $23m. Or maybe there were darker forces at play: Hollinghurst's publisher, Macmillan, is contesting the US Justice Department's ruling that the doomed "agency model" – where publishers, not retailers, control pricing – led to price-fixing. Was this a show of strength by Amazon?

The true story, uncovered by the Bookseller, is even murkier. Sony is challenging Amazon's dominance of the cheap ebook market by offering a range of 20p titles in its new Reader Store. It has convinced three publishers, including Macmillan, to take part, and all Amazon is doing is price-matching: more John Lewis than playground bully.

Publishers' willingness to experiment makes a change from the insistence that price be determined by the effort that goes into producing something, and no doubt they're enjoying the roaring sales. But by letting their ebooks practically be given away, they are complicit in eroding the value of their product. Macmillan's CEO, John Sargent, recently warned that books are "in danger of becoming roadkill" in a digital war. It will be hard to tell who ran them over.